I would go with Sylars general information as I know of my own experimenting that exactly that is the case independant of the hardware which of course doesn't have to do with the maximum polycount. Thehardware is only important for the speed of your scripts and so and thus also don't penetrade with the polycount number.
I agree, I can have 16 fullscreen shader effects, and that does not drop my FPS... unless ofcourse I go over the max poly count as stated by Sylar.
